The relation between the ¹⁸O and deuterium contents of rain water in the Negev Desert and air-mass trajectories

Sampling of rain water was carried out in the Negev, Israel, from 1978 till 1981, by means of a self-sealing sampler which enables the sampling of each separate rain storm, as well as parts of each storm. The relation between the isotopic composition and various synoptic parameters is discussed. Based on “deuterium excess” values, the rain samples can be separated into three groups. The majority of the samples have a “deuterium excess” between 10 and 22‰. These samples have different histories from the meteorological point of view. However, there are two extreme groups, one has “deuterium excess” values above 22‰ and the other has values less than 10‰. It was found that the rains which are most depleted with regard to deuterium and with the lowest “deuterium excess” values are associated with air masses that reach the region concerned from the southwest. Rains with a “deuterium excess” of more than 22‰ are associated with air masses which come mainly from northeastern Europe and reach the considered region from west to northwest, following intense interaction with the central-eastern Mediterranean Sea.